Dispersible flushable moist products must exhibit satisfactory in-use strength, but quickly break down in sewer or septic systems. Current flushable moist wipes do this by using a triggerable salt sensitive binder on a substrate comprising cellulose based fibers. The binder attaches to cellulose fibers which form a network of in-use strength in a salt solution (used as the moist wipe formulation), but swells and falls apart in the fresh water of the toilet and sewer system.
Additionally, flushable moist wipes need to easily pass through current municipal sewer systems. For many years, the problem of disposability has plagued industries that provide disposable items, such as diapers, wet wipes, incontinence garments and feminine care products. Ideally, when a flushable disposable product is discarded in either sewer or septic systems, the product, or designated portions of the product, should “disperse” and thus sufficiently dissolve or disintegrate in water so as not to present problems under conditions typically found in household and municipal sanitization systems. Some products have failed to properly disperse. Many current wipe manufacturers achieve acceptable strength in flushable moist wipes by using long fibers (>10 mm) which entangle with other fibers to develop a wet strength network. However, these long fibers are not desirable because they tend to collect on screens in waste water systems and cause obstructions and blockages.
In response to increased concerns for blockages, INDA/EDANA published guidelines for assessing flushability of nonwoven consumer products, the scope of the document covering flushable moist wipes. By following these guidelines, manufacturers can ensure that under normal usage conditions products best disposed of via the waste water systems for public health and hygiene reasons will not block toilets, drainage pipes, water conveyance and treatments systems or become an aesthetic nuisance in surface waters or soil environments.
One challenge for flushable moist wipes is that it takes much longer to break down when compared to dry toilet tissue potentially creating issues in sewer or septic systems. Currently dry toilet tissue quickly exhibits lower post-use strength when exposed to tap water whereas current flushable moist wipes take time and/or agitation.
To achieve faster dispersion times with current binder technologies requires lower in-use strength that is deemed unacceptable by current consumers. Dispersibility could also be improved by curing/drying the binder less, but again provides unacceptable in-use strength. High density thin tissue webs with short fibers have been used to prepare wipes as well.
However, one problem with these wipes formed from a thin, dense and compact single ply is that such wipes tend to lack the superior softness that is desired by consumers. Further, the bulk and resiliency of such wipes is less than desirable. A single ply tissue web does not provide the smooth, bulky, resilient feel that consumers prefer in tissues of this type.
Other manufactures use shorter fibers in an airlaid nonwoven structure and bond them together with binder. However, at low densities, large amounts of binder are needed to bond the widely spaced network and this results in a relatively stiff, nonconformable sheet, and if the density is increased to reduce the binder needed the sheet loses stretch, thickness and softness.
What is needed in the industry is a multi-ply product that is durable and soft having increased resiliency and enhanced substance in hand. Unfortunately, these approaches to addressing the dispersibility problems above provide unacceptable strength or products that do not disperse quickly enough. Thus, there is a need to provide a wet wipe that provides proper in-use strength for consumers and still feels soft and comfortable, but disperses more like toilet paper to pass various municipal regulations and be defined as a flushable product.